Method of spinning high tenacity viscose rayon



Patented Get. 26, 1948 'METHOD 'O-F SPINNING. HIGH TENACITY VIS C S E RAYON Guillaume M. A. Kayser, Arnhem, Netherlands, assignor to American Enka Corporation, Erika, N. 0., .a corporation of Delaware No Drawing. Application April 1,1946, Serial No. 658,865. In'Germany December 1.6, 1943 Section 1, Public Law 690, August 8, 1946 Patent expires December 16, 1963 Claims.

1 The present invention relates to the manufacture of viscose rayon and more particularly to a process in which rayon threads formed from visoose are precipitated in an acid spinbath and subsequently highly stretched in a hot dilute acid bath in order to increase the strength of the threads.

It is, of -course,'we1-l known at the present time that the strength-of viscose yarn can be increased by stretching the same, preferably within a short time after it leaves the spinbath, and the strength increases in direct proportion to the increase in stretch. The system generally'used is known as the two-bath spinning process, and includes a normal spinbath containing sulphuric acid and salts such as sodium sulphate, magnesium suiphate and zinc sulphate, and a second bath which is maintained at a high temperature, for example, in the neighborhood of 90 C. At this temperature, a high degree of stretch can be imparted to the thread during its passage therethrough. This secpnd hot bath is weakly acid as a result of a small amount of acid being carried over from the spinbath by the thread and inpractice, preferably should not exceed 2 sul-- phuric acid. The stretching in the second bath is effected by means of friction guides or between two or more disks or rollers or similar devices driven at different speeds. Although the stretchability of the thread :is increased when using this twobath process, the stretch is limited to a fixed value. It cannot exceed the breaking point of the thread and therefore the point at which the thread-break occurs determines the maximum stretch and maximum increaserin strength.

It has now been determined that it is possible to increase the stretchability of the thread and thereby exceed the maximum stretch possible in.

the above mentioned normal: two-bath spinning process,'and by so doing, increase the strength of the viscose threads. This may be done by subjecting the threads to the influence of a small amount of an aliphatic aldehyde prior to highly stretching the thread in a hot bath. In particular, it has been determined that formaldehyde is especially suitable in the process and may be added to the acid spinbath, or if more'than two baths are employed, for example, if a water bath maintained at the temperature of the spinbath is interposed between the spinbath and the hot bath, the formaldehyde may be added to the water bath.

When formaldehyde is added to the spinbath or the water bath and the thread is subsequently stretched, considerably improved results are obtained. If other conditions are the same, ahigh stretch, that would normally cause fluff-formation as a result of partial rupturing of the filaments without the use of formaldehyde, will not cause these undesirable results when formaldehyde is added. Furthermore, for any given stretch, the use of formaldehyde lowers the ten-' sion in the thread.

The following table represents the observations of a series of experiments using increasing.

amounts of formaldehyde whereby the tension was always measuredat'a stretch of60% and80% and the stretch limit was also determined. The experiments were conducted using a spinbath of the following composition: (The parts are by weight.) 7% sulphuric acid,,.1i7% sodium sulphate, 4% magnesium sulphate, and 0.7% zinc sulphate, to which increasing percentages of formaldehyde were added as shown in the first column of the table. The formaldehyde was added in the form of a 40% aqueous solution, of which the quantity was always taken 2 times greater:

Table Formaldehydejgwgcentage of the stretch Tension Percent G. Per cent 0 i 35 .90

v 2.'0. s .l... .ews. 60 10. 40 80 22 Example 1 amount of acid as a result of the carrying along y of spinbath by the thread, which amount of acid After leaving this bath iii in practice was not allowed to exceed 2% sulphuric acid. In this bath the thread was stretched 120% by means of driven rollers. Thereupon the thread was led into a centrifuge and after the formation of a spinning cake was washed in the customary manner, given aftertreatments and dried. The dry strength of the yarn thus obtained was 350 grams per 100 denier.

In a control test in which no formaldehyde was added to the spinbath, the thread in the hot water bath could not be stretched more than 80%, whereupon the dry strength of the thread made under otherwise similar conditions was only 300 grams per 100 denier.

Example 2 A viscose of 8% cellulose and 7% alkali content and 33% carbon disulphide was ripened for 20 hours at 10 C. The spinning viscosity was then 55. It was spun into a thread of 100 denier and 40 filaments. The spinbath contained 9% sulphuric acid, 18% sodium sulphate, 5%

magnesium sulphate, 1% zinc sulphate, and 2% formaldehyde. After leaving this bath, the freshly spun thread was led through a water bath heated to 90 C. which contained a small amount of acid as a result of the carrying along of the spinbath by the thread, which amount of acid was kept-below 2% sulphuric acid. In this bath the thread was stretched 110% and thereafter collected on a spool. The dry strength of the after-treated and dried thread was 407 grams per 100 denier.

In a control test in which no formaldehyde was added to the spinbath, the thread in the second hot water bath could only be stretched 70%, whereupon the dry strength of the thread, made under otherwise similar conditions, was only 330 grams per 100 denier.

As it is known to use formaldehyde in aftertreatments of rayon and to use formaldehyde in combination with special types of spinbaths both for other purposes, no claim is here made to such uses. The use herein is restricted to systems using two or three baths for the purpose of inviscose rayon involving the use of a precipitating bath, and a hot bath in which the rayon is highly stretched which comprises subjecting the rayon to the influence of a small amount of formaldehyde prior to the high stretching effected in the hot bath.

2. A method of manufacturing high tenacity viscose rayon involving the use of the two-bath system which comprises spinning the rayon in a precipitating bath containing sulphuric acid and salts and to which has been added a small amount of formaldehyde, passing the rayon to a second hot, dilute acid bath and during the passage therethrough effecting a high stretch on the rayon.

3. A method of manufacturing high tenacity viscose rayon involving the use of the two-bath system which comprises spinning the rayon in a precipitating bath containing sulphuric acid and salts and to which has been added not more than 2% formaldehyde based on the weight of the bath, passing the rayon to a second hot, dilute acid bath and during the passage therethrough effecting a high stretch on the rayon.

4. A method of manufacturing high tenacity viscose rayon which comprises coagulating. the rayon in a spinbath containing sulphuric acidand salts, passing the rayon through-a water bath containing not morethan 2% formaldehyde'based on-the weight of the bath, and finallystretching the rayon while passing the same through a hot bath maintained at a temperature in the neighborhoodof 90 C.

5. .A method manufacturing high tenacity viscose rayonyarn and the like involving the use of the two-bath system which comprises spinning the yarn in a precipitating bath containing sulphuric acid, metallic salts and about 2% formaldehyde, passing the yarn to a second aqueous bath containing less than 2% H2304 and main-- tained at a temperature in the neighborhood of 90 C. and, during the passage Of the yarn there'- REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number 1 Name Date 2,348,415 Polak May 9, 1944 FOREIGN PATENTS Number Country Date 439,359 Germany Jan. 8,1927

335,605 Great Britain June 27, 1929 

